$ { \left[\begin{array}{rr}{2} & {4} \\ {2} & {-2} \\ {-1} & {-2}\end{array}\right]+\left[\begin{array}{rr}{-1} & {1} \\ {4} & {1} \\ {-1} & {-1}\end{array}\right] = {?} } $
Solution: To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{rr}{2}+{-1} & {4}+{1} \\ {2}+{4} & {-2}+{1} \\ {-1}+{-1} & {-2}+{-1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{1} & {5} \\ {6} & {-1} \\ {-2} & {-3}\end{array}\right]}$